3 When they blow them, all the congregation shall gather themselves to you at the door of the Tent of Meeting.
*Minor differences ignored. Grouped by changes, with first version listed as example.
And when they shall blow with them,.... With both the trumpets, in an even and continued sound, that is, the sons of Aaron:
all the assembly shall assemble themselves to thee at the door of the tabernacle of the congregation; to hear what was to be said unto them: blowing both the trumpets together was a token that the whole congregation was called to meet together at the tabernacle, the door of which was the usual place of assembling, especially on religious counts, for there also the Lord met them, Exodus 29:42.
when they shall blow with them--There seem to have been signals made by a difference in the loudness and variety in the notes, suited for different occasions, and which the Israelites learned to distinguish. A simple uniform sound by both trumpets summoned a general assembly of the people; the blast of a single trumpet convoked the princes to consult on public affairs; notes of some other kind were made to sound an alarm, whether for journeying or for war. One alarm was the recognized signal for the eastern division of the camp (the tribes of Judah, Issachar, and Zebulun) to march; two alarms gave the signal for the southern to move; and, though it is not in our present Hebrew text, the Septuagint has, that on three alarms being sounded, those on the west; while on four blasts, those on the north decamped. Thus the greatest order and discipline were established in the Israelitish camp--no military march could be better regulated.
*More commentary available at chapter level.